pointers

[fressanme]

can anyone give me a concise and an easy-to-understand discussion on pointers? ive been reading about pointers for months now and still i dont clearly understand how to use it..a short discussion and example will do..thanks!

[Laharl]

Try this and see if it helps.

[JosAH]

a short discussion and example will do..thanks!

Example:

[code=c]
char * cp;
[/code]

Short discussion:

Oh my, I think I just saw a pointer out there!
You did? No you didn't!
Yes I did and it was a nice char(ming) pointer as well!
No you did not!
Yes I did!
You did not!
I did!
Did not! It was an ugly pointer as they all are!
Did!
Did not!!!!
Did! Did! Did!
Dit not! A slimey pointer! Don't trust them!
I did see it!
Did not!
Did!
...

kind regards,

Jos ;-)

[weaknessforcats]

You already know how to use pointers. You do it every day.

Example: You are invited to a party at 123 Center Ave at 7pm.

When you write this address on a piece of paper so you don't forget it, the paper becomes a pointer containing the address of a party. That is, the paper is a Party*. The actual party at that location (123 Center Ave), is a variable.

So the procedure is:

1) Create a piece of paper (the pointer variable)

Party* ptr;

2) Create a party variable:

struct Party
{
char* whattobring;
};

Party Fri7pm;

3) Write the address of the party on the paper:

ptr = &Fri7pm;

4) Determine what to bring indirectly using the pointer:

ptr->whattobring

OR:

(*ptr).whattobr ing

Orignially, C designed the syntax this way;

int a, b, c;

Here a, b, and c are ints.

Then they did this:

int a,b,c, *d;

Here a,b,c and *d are ints.

d is the pointer variable that is to contain the address of an int. *d is that int.

You use pointers so you can determine what to do indirectly. Say to compare two struct variables. You write a function that takes two pointer arguments. That way the function can compare any two variables without needing to make a copy of the variables.

You also use pointers so a function can change the contents of a variable that's not part of the function. You do this by passing in the address of the variable in a pointer. The function de-references the pointer and makes the change at the address contained in the pointer. Again, this avoids having to make a copy of the variable as a local variable, make the change in the local copy and then make a copy of the local copy to return.